Re-invite Without SDP

Hello All,

I am facing the issue with one of my customer at the time of unhold the
call.

I have configured an endpoint that is dropping calls when you place the call
on hold.

The network configuration is as follows:

Cisco CallManager using SIP signaling > Cisco Unified Border Element (CUBE)
using SIP signaling > MSX communicates SIP to CUBE and h.323 to
HT_5850_Egress > PSTN

When a phone on the Cisco CallManager places a call to a user on the PSTN
the call goes through successfully. When the phone on the Cisco CallManager
places that call on hold, the call gets dropped.

The message I see in the SIP trace is '488 Not acceptable here'.

If we do this same test from the Call Manager to the CUBE to the MSX but
instead to L3_Egress so the signalling between the CUBE/MSX/PSTN is SIP the
hold option works.

*First IWF.. Where this option is not working.

*Calling number 763.432.8682
Called number 763.577.3948


On this First Source UA has send the initial invite and which SBC has sent
to termination END as h.323 and call is connected successully after the the
mesages... Now when my Source UA has sent the invite to put that call on
hold it sends "*re-invite with SDP with codec g.711u and media attribute =
inactive*", and call goes on hold successfully, but now whenever they are
trying to unhold the call and sending the another "*invite without sdp*"
than my SBC/Nextone is sending "*488 unacceptable*" to my source UA.

*And now the other option SIP(both legs)*

Calling number 763.432.8682
Called number 1612.964.8862

Now in this scenario i have both the legs on sip and when my source UA is
sending the "invite without SDP" to unhold this call then my my termination
end is sending 200 OK with SDP to ACK that call and unhold scenario is
working fine.

I am also attaching the call flow for both the scenario. Please help me to
find out the root cause of this issue.

Thanks,
Nitin Kapoor
General Telecom

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